Correct URLs to project homepage

This commit adds 'http://' back to the project URLs so that the links actually
work.
Edit README file for project

This commit moves the information about compiling the pdfs earlier in the
pdf.  It also lists additional instructions for compiling them without latexmk
or make and adds more prominant download links.
Add placeholder VERSION.tex and CITATION.bib files

This commit adds templates for VERSION.tex and CITATION.bib: those
files are automatically generated by the makefile to contain the
date and version of the current commit.  Unfortunately, this means
that they do not exist when the repository is first cloned, which
causes errors in LaTeX.  So this commit adds files that explain
that they are just placeholders and gives directions for how to
determine the correct information.  I've also added those directions
to the README file.
Add macro to automate BibTeX typesetting
Add 'http' prefix back to the GNU FDL homepage

Some pdf readers (i.e. Konqueror) wouldn't follow the link
to the GNU homepage without an 'http://' prefix.
Move FDL and author list into the individual pdf files

In earlier versions, we viewed the collection of pdfs as a single
entity and encouraged the FDL and author lists to be distributed
as separate pdf files (to minimize space and duplication).  But
it does seem likely that people will encounter these pdfs separately,
so we've decided to include the license and author list in every
pdf by default.

I still think that our earlier view is correct and that the license
and author list can be distributed once (for example, if the book
is used for a class, the instructor can compile the pdfs without
licensing information, but just give the license to the students
the first day), so this is just a matter of emphasis.
Change linear regression file to 'regression'
Release version 0.3.2

A housekeeping release, mostly:
* Adds the 'http://' prefix back to URLs so that they work in more pdf
  readers
* Updates the README file with more useful directions on compiling
  pdfs
* Adds placeholder files for version and citation information to
  prevent compilation errors
* Changes to include the author list and license in each pdf by
  default
* Renames the linear regression file